Imaging lens

ABSTRACT

There is provided an imaging lens with excellent optical characteristics which satisfies demand of the wide field of view, the low-profileness and the low F-number. An imaging lens comprises, in order from an object side to an image side, a first lens with positive refractive power having a convex surface facing the object side near an optical axis, a second lens having negative refractive power near the optical axis, a third lens, a fourth lens, and a fifth lens with the negative refractive power having a concave surface facing the image side near the optical axis, wherein an image-side surface of the fifth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and predetermined conditional expressions are satisfied.

The present application is based on and claims priority of a Japanesepatent application No. 2018-115908 filed on Jun. 19, 2018, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an imaging lens which forms an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in an imaging device, and more particularly relates to animaging lens which is built in a smartphone and a mobile phone whichbecome increasingly compact and excellent in performance, an informationterminal such as a PDA (Personal Digital Assistant), a game console, PCand a robot, and moreover, a home appliance with camera function, amonitoring camera and an automobile.

Description of the Related Art

In recent years, it becomes common that camera function is mounted in ahome appliance, information terminal equipment, an automobile and publictransportation. Demand of products with the camera function is moreincreased, and development of various products is being madeaccordingly.

The imaging lens mounted in such equipment is required to be compact andto have high-resolution performance.

As a conventional imaging lens aiming high performance, for example, theimaging lens disclosed in Patent Document 1 (WO2014/119283) has beenknown.

Patent Document 1 discloses an imaging lens comprising, in order from anobject side, a first lens with positive refractive power having ameniscus shape including a convex surface facing the object side, asecond lens with negative refractive power having a biconcave shape, athird lens with positive refractive power, a fourth lens with thepositive refractive power, and a fifth lens with the negative refractivepower having a biconcave shape.

SUMMARY OF THE INVENTION

However, in lens configurations disclosed in the Patent Document 1, whenwide field of view, low-profileness and low F-number are to be realized,it is very difficult to correct aberrations at a peripheral area, andexcellent optical performance can not be obtained.

The present invention has been made in view of the above-describedproblems, and an object of the present invention is to provide animaging lens with high resolution which satisfies demand of the widefield of view, the low-profileness and the low F-number in well balanceand excellently corrects aberrations.

Regarding terms used in the present invention, “a convex surface”, “aconcave surface” or “a plane surface” of lens surfaces implies that ashape of the lens surface near an optical axis (paraxial portion).“Refractive power” implies the refractive power near the optical axis.“A pole point” implies an off-axial point on an aspheric surface atwhich a tangential plane intersects the optical axis perpendicularly. “ATotal track length” is defined as a distance along the optical axis froman object-side surface of an optical element located closest to theobject to an image plane. “The total track length” and “a back focus” isa distance obtained when thickness of an IR cut filter or a cover glasswhich may be arranged between the imaging lens and the image plane isconverted into an air-converted distance.

An imaging lens according to the present invention comprises, in orderfrom an object side to an image side, a first lens with positiverefractive power having a convex surface facing the object side near anoptical axis, a second lens having negative refractive power near theoptical axis, a third lens, a fourth lens, a fifth lens with thenegative refractive power having a concave surface facing the image sidenear the optical axis, wherein an image-side surface of the fifth lensis formed as an aspheric surface having at least one pole point in aposition off the optical axis.

According to the imaging lens having the above-described configuration,the first lens properly corrects spherical aberration and distortion byhaving the convex surface facing the object side near the optical axis.The second lens properly corrects the spherical aberration occurring atthe first lens and chromatic aberration. The third lens properlycorrects aberrations at a peripheral area. The fourth lens properlycorrects astigmatism, field curvature and the distortion. The fifth lensproperly corrects the chromatic aberration, the astigmatism, the fieldcurvature and the distortion. An image-side surface of the fifth lens isa concave surface facing the image side near the optical axis, and byforming as the aspheric surface having at least one pole point in aposition off the optical axis, the field curvature and the distortioncan be properly corrected and a light ray incident angle to an imagesensor can be properly controlled.

According to the imaging lens having the above-described configuration,it is preferable that an image-side surface of the first lens is aconcave surface facing the image side near the optical axis.

When the image-side surface of the first lens is the concave surfacefacing the image side near the optical axis, the astigmatism and thedistortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that an object-side surface of the second lens is aconvex surface facing the object side near the optical axis.

When the object-side surface of the second lens is the convex surfacefacing the object side near the optical axis, the astigmatism and thedistortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that the fourth lens has the positive refractive powernear the optical axis.

When the refractive power of the fourth lens is positive, thelow-profileness is more facilitated.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (1) is satisfied:

10.00<νd3<39.00  (1)

whereνd3: an abbe number at d-ray of the third lens.

The conditional expression (1) defines an appropriate range of the abbenumber at d-ray of the third lens. By satisfying the conditionalexpression (1), the chromatic aberration can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (2) is satisfied:

0.25<T2/T3<1.00  (2)

whereT2: a distance along the optical axis from an image-side surface of thesecond lens to an object-side surface of the third lens, andT3: a distance along the optical axis from an image-side surface of thethird lens to an object-side surface of the fourth lens.

The conditional expression (2) defines an appropriate range of adistance between the second lens and the third lens and a distancebetween the third lens and the fourth lens. By satisfying theconditional expression (2), difference of the distance between thesecond lens and the third lens and the distance between the third lensand the fourth lens is suppressed from being large, and thelow-profileness is achieved. Furthermore, by satisfying the conditionalexpression (2), the third lens is arranged at an optimum position, andaberration correction function of the lens becomes more effective.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (3) is satisfied:

0.50<r2/f<1.65  (3)

wherer2: paraxial curvature radius of an image-side surface of the firstlens, andf: a focal length of the overall optical system of the imaging lens.

The conditional expression (3) defines an appropriate range of theparaxial curvature radius of the image-side surface of the first lens.When a value is below the upper limit of the conditional expression (3),the astigmatism can be properly corrected. On the other hand, when thevalue is above the lower limit of the conditional expression (3), thespherical aberration occurring at this surface is suppressed andsensitivity to a manufacturing error can be easily reduced, whilemaintaining the refractive power of the image-side surface of the firstlens.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (4) is satisfied:

−5.00<r9/r10<−2.20  (4)

wherer9: paraxial curvature radius of an object-side surface of the fifthlens, andr10: paraxial curvature radius of an image-side surface of the fifthlens.

The conditional expression (4) defines relationship between paraxialcurvature radii of the object-side surface and the image-side surface ofthe fifth lens. By satisfying the conditional expression (4), thespherical aberration, the astigmatism and the distortion can be properlycorrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (5) is satisfied:

1.90<(T4/f)×100<10.00  (5)

whereT4: a distance along the optical axis from an image-side surface of thefourth lens to an object-side surface of the fifth lens, andf: a focal length of the overall optical system of the imaging lens.

The conditional expression (5) defines an appropriate range of adistance along the optical axis between the fourth lens and the fifthlens. By satisfying the conditional expression (5), the distortion canbe properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (6) is satisfied:

1.20<T2/T1<7.00  (6)

whereT2: a distance along the optical axis from an image-side surface of thesecond lens to an object-side surface of the third lens, andT1: a distance along the optical axis from an image-side surface of thefirst lens to an object-side surface of the second lens.

The conditional expression (6) defines an appropriate range of adistance between the second lens and the third lens and a distancebetween the first lens and the second lens. By satisfying theconditional expression (6), difference of the distance between thesecond lens and the third lens and the distance between the first lensand the second lens is suppressed from being large, and thelow-profileness is achieved. Furthermore, by satisfying the conditionalexpression (6), the second lens is arranged at an optimum position, andaberration correction function of the lens becomes more effective.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (7) is satisfied:

1.10<T3/T4<5.50  (7)

whereT3: a distance along the optical axis from an image-side surface of thethird lens to an object-side surface of the fourth lens, andT4: a distance along the optical axis from an image-side surface of thefourth lens to an object-side surface of the fifth lens.

The conditional expression (7) defines an appropriate range of adistance between the third lens and the fourth lens and a distancebetween the fourth lens and the fifth lens. By satisfying theconditional expression (7), difference of the distance between the thirdlens and the fourth lens and a distance between the fourth lens and thefifth lens is suppressed from being large, and the low-profileness isachieved. Furthermore, by satisfying the conditional expression (7), thefourth lens is arranged at an optimum position, and aberrationcorrection function of the lens becomes more effective.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (8) is satisfied:

2.30<D1/D2<3.80  (8)

whereD1: a thickness along the optical axis of the first lens, and D2: athickness along the optical axis of the second lens.

The conditional expression (8) defines an appropriate range of thethickness along the optical axis of the first lens and the thicknessalong the optical axis of the second lens. When a value is below theupper limit of the conditional expression (8), the distortion can beproperly corrected. On the other hand, when the value is above the lowerlimit of the conditional expression (8), the spherical aberration, comaaberration and the astigmatism can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (9) is satisfied:

0.50<r3/f<9.00  (9)

wherer3: paraxial curvature radius of an object-side surface of the secondlens, andf: a focal length of the overall optical system of the imaging lens.

The conditional expression (9) defines an appropriate range of theparaxial curvature radius of the object-side surface of the second lens.When a value is below the upper limit of the conditional expression (9),the astigmatism and the coma aberration can be properly corrected. Onthe other hand, when the value is above the lower limit of theconditional expression (9), the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (10) is satisfied:

0.35<r4/f<1.25  (10)

wherer4: paraxial curvature radius of an image-side surface of the secondlens, andf: a focal length of the overall optical system of the imaging lens.

The conditional expression (10) defines an appropriate range of theparaxial curvature radius of the image-side surface of the second lens.When a value is below the upper limit of the conditional expression(10), the astigmatism and the distortion can be properly corrected. Onthe other hand, when the value is above the lower limit of theconditional expression (10), the spherical aberration can be properlycorrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (11) is satisfied:

−2.30<r9/f<−0.85  (11)

wherer9: paraxial curvature radius of an object-side surface of the fifthlens, andf: a focal length of the overall optical system of the imaging lens.

The conditional expression (11) defines an appropriate range of theparaxial curvature radius of the object-side surface of the fifth lens.When a value is below the upper limit of the conditional expression(11), the spherical aberration can be properly corrected. On the otherhand, when the value is above the lower limit of the conditionalexpression (11), the astigmatism, the field curvature and the distortioncan be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (12) is satisfied:

0.20<r2/r3<1.30  (12)

wherer2: paraxial curvature radius of an image-side surface of the firstlens, andr3: paraxial curvature radius of an object-side surface of the secondlens.

The conditional expression (12) defines relationship between theparaxial curvature radius of the image-side surface of the first lensand the paraxial curvature radius of the object-side surface of thesecond lens. By satisfying the conditional expression (12), theastigmatism and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (13) is satisfied:

1.00<r3/r4<9.50  (13)

wherer3: paraxial curvature radius of an object-side surface of the secondlens, andr4: paraxial curvature radius of an image-side surface of the secondlens.

The conditional expression (13) defines relationship between paraxialcurvature radii of the object-side surface and the image-side surface ofthe second lens. By satisfying the conditional expression (13), theastigmatism and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (14) is satisfied:

1.65<Nd2  (14)

whereNd2: refractive index at d-ray of the second lens.

The conditional expression (14) defines an appropriate range of therefractive index at d-ray of the second lens. By satisfying theconditional expression (14), the chromatic aberration can be properlycorrected and a low-cost plastic material can be selected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (15) is satisfied:

1.60<Nd3<1.70  (15)

whereNd3: refractive index at d-ray of the third lens.

The conditional expression (15) defines an appropriate range of therefractive index at d-ray of the third lens. By satisfying theconditional expression (15), the chromatic aberration can be properlycorrected and a low-cost plastic material can be selected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (16) is satisfied:

TTL/EPd2.50  (16)

whereTTL: a total track length, andEPd: an entrance pupil diameter.

The conditional expression (16) defines relationship between the totaltrack length and the entrance pupil diameter. By satisfying theconditional expression (16), the total track length can be shortened,decrease in light quantity at the peripheral area can be suppressed andan image having sufficient brightness from a center to a peripheral areacan be obtained.

According to the imaging lens having the above-described configuration,it is preferable that composite refractive power of the fourth lens andthe fifth lens is negative, and more preferable that a below conditionalexpression (17) is satisfied:

−22.00<f45/f<−1.50  (17)

wheref45: a composite focal length of the fourth lens and the fifth lens, andf: a focal length of the overall optical system of the imaging lens.

When the composite refractive power of the fourth lens and the fifthlens is negative, it is favorable for correction of the chromaticaberration. The conditional expression (17) defines an appropriate rangeof the composite refractive power of the fourth lens and the fifth lens.When a value is below the upper limit of the conditional expression(17), the negative composite refractive power of the fourth lens and thefifth lens becomes appropriate, and the low-profileness can be achieved.On the other hand, when the value is above the lower limit of theconditional expression (17), the astigmatism, the field curvature andthe distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (18) is satisfied:

3.50<(T2/f)×100<10.00  (18)

whereT2: a distance along the optical axis from an image-side surface of thesecond lens to an object-side surface of the third lens,f: a focal length of the overall optical system of the imaging lens.

The conditional expression (18) defines an appropriate range of adistance along the optical axis between the second lens and the thirdlens. By satisfying the conditional expression (18), the astigmatism andthe field curvature can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (19) is satisfied:

0.30<D2/D3<0.75  (19)

whereD2: a thickness along the optical axis of the second lens, andD3: a thickness along the optical axis of the third lens.

The conditional expression (19) defines an appropriate range of thethickness along the optical axis of the second lens and the thicknessalong the optical axis of the third lens. By satisfying the conditionalexpression (19), the astigmatism and the distortion can be properlycorrected.

Effect of Invention

According to the present invention, there can be provided an imaginglens with high resolution which satisfies demand of the wide field ofview, the low-profileness and the low F-number in well balance, andproperly corrects aberrations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an imaging lens in Example 1according to the present invention;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1 according to the present invention;

FIG. 3 is a schematic view showing an imaging lens in Example 2according to the present invention;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2 according to the present invention;

FIG. 5 is a schematic view showing an imaging lens in Example 3according to the present invention;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3 according to the present invention;

FIG. 7 is a schematic view showing an imaging lens in Example 4according to the present invention;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4 according to the present invention;

FIG. 9 is a schematic view showing an imaging lens in Example 5according to the present invention;

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5 according to the present invention;

FIG. 11 is a schematic view showing an imaging lens in Example 6according to the present invention;

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6 according to the present invention;

FIG. 13 is a schematic view showing an imaging lens in Example 7according to the present invention;

FIG. 14 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 7 according to the present invention;

FIG. 15 is a schematic view showing an imaging lens in Example 8according to the present invention; and

FIG. 16 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 8 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the preferred embodiments of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5, 7, 9, 11, 13 and 15 are schematic views of the imaginglenses in Examples 1 to 8 according to the embodiments of the presentinvention, respectively.

As shown in FIG. 1, the imaging lens according to the present embodimentcomprises, in order from an object side to an image side, a first lensL1 with positive refractive power having a convex surface facing theobject side near an optical axis X, a second lens L2 having negativerefractive power near the optical axis X, a third lens L3, a fourth lensL4, and a fifth lens L5 with the negative refractive power having aconcave surface facing the image side near the optical axis X. Animage-side surface of the fifth lens L5 is formed as an aspheric surfacehaving at least one pole point in a position off the optical axis X.

A filter IR such as an IR cut filter and a cover glass are arrangedbetween the fifth lens L5 and an image plane IMG (namely, the imageplane of an image sensor). The filter IR is omissible.

By arranging an aperture stop ST on the object side of the first lensL1, correction of aberrations and control of an incident angle of thelight ray of high image height to the image sensor become facilitated.

The first lens L1 has the positive refractive power and has a meniscusshape having a convex surface facing the object side and a concavesurface facing the image side near the optical axis X. Therefore,spherical aberration, astigmatism and distortion can be properlycorrected.

The second lens L2 has the negative refractive power and has a meniscusshape having a convex surface facing the object side and a concavesurface facing the image side near the optical axis X. Therefore, thespherical aberration, chromatic aberration, the astigmatism and thedistortion can be properly corrected.

The third lens L3 has the positive refractive power and has a biconvexshape having convex surfaces facing the object side and the image sidenear the optical axis X. Therefore, the astigmatism and the distortioncan be properly corrected. Furthermore, a configuration of the biconvexshape suppresses curvature from being large, and reduces sensitivity toa manufacturing error. A shape of the third lens L3 may be a meniscusshape having the convex surface facing the object side and the concavesurface facing the image side near the optical axis X as in the Examples2 and 3 shown in FIGS. 3 and 5. In this case, coma aberration and fieldcurvature can be properly corrected. Furthermore, as in the Examples 4to 8 shown in FIGS. 7, 9, 11, 13 and 15, the third lens may have a shapehaving plane surfaces facing the object side and the image side near theoptical axis X and substantially having no refractive power near theoptical axis X. In this case, the astigmatism, the field curvature andthe distortion at a peripheral area can be properly corrected by theaspheric surfaces on both sides without affecting a focal length of theoverall optical system of the imaging lens or refractive powerdistribution of other lenses.

The fourth lens L4 has the positive refractive power and has a meniscusshape having a concave surface facing the object side and a convexsurface facing the image side near the optical axis X. Therefore, alight ray incident angle to the fourth lens L4 becomes appropriate, andthe astigmatism, the field curvature and the distortion can be properlycorrected.

The fifth lens L5 has the negative refractive power and has a biconcaveshape having concave surfaces facing the object side and the image sidenear the optical axis X. Therefore, the chromatic aberration, theastigmatism, the field curvature and the distortion can be properlycorrected. Furthermore, a configuration of the biconcave shapesuppresses curvature from being large, and reduces sensitivity to amanufacturing error.

Regarding the imaging lens according to the present embodiments, it ispreferable that all lenses of the first lens L1 to the fifth lens L5 aresingle lenses. Configuration only with the single lenses can frequentlyuse the aspheric surfaces. In the present embodiments, all lens surfacesare formed as appropriate aspheric surfaces, and the aberrations arefavorably corrected. Furthermore, in comparison with the case in which acemented lens is used, workload is reduced, and manufacturing in lowcost becomes possible.

Furthermore, the imaging lens according to the present embodiments makesmanufacturing facilitated by using plastic material for all lenses, andmass production in a low cost can be realized.

The material applied to the lens is not limited to the plastic material.By using glass material, further high performance may be aimed. It ispreferable that all of lens-surfaces are formed as aspheric surfaces,however, spherical surfaces easy to be manufactured may be adopted inaccordance with required performance.

The imaging lens according to the present embodiments shows preferableeffect by satisfying the below conditional expressions (1) to (19).

10.00<νd3<39.00  (1)

0.25<T2/T3<1.00  (2)

0.50<r2/f<1.65  (3)

−5.00<r9/r10<−2.20  (4)

1.90<(T4/f)×100<10.00  (5)

1.20<T2/T1<7.00  (6)

1.10<T3/T4<5.50  (7)

2.30<D1/D2<3.80  (8)

0.50<r3/f<9.00  (9)

0.35<r4/f<1.25  (10)

−2.30<r9/f<−0.85  (11)

0.20<r2/r3<1.30  (12)

1.00<r3/r4<9.50  (13)

1.65<Nd2  (14)

1.60<Nd3<1.70  (15)

TTL/EPd2.50  (16)

−22.00<f45/f<−1.50  (17)

3.50<(T2/f)×100<10.00  (18)

0.30<D2/D3<0.75  (19)

whereNd2: refractive index at d-ray of the second lens L2,Nd3: refractive index at d-ray of the third lens L3,νd3: an abbe number at d-ray of the third lens L3,D1: a thickness along the optical axis X of the first lens L1,D2: a thickness along the optical axis X of the second lens L2,D3: a thickness along the optical axis X of the third lens L3,T1: a distance along the optical axis X from an image-side surface ofthe first lens L1 to an object-side surface of the second lens L2,T2: a distance along the optical axis X from an image-side surface ofthe second lens L2 to an object-side surface of the third lens L3,T3: a distance along the optical axis X from an image-side surface ofthe third lens L3 to an object-side surface of the fourth lens L4,T4: a distance along the optical axis X from an image-side surface ofthe fourth lens L4 to an object-side surface of the fifth lens L5,TTL: a total track length,EPd: an entrance pupil diameter,f: a focal length of the overall optical system of the imaging lens,f45: a composite focal length of the fourth lens L4 and the fifth lensL5,r2: paraxial curvature radius of an image-side surface of the first lensL1,r3: paraxial curvature radius of an object-side surface of the secondlens L2,r4: paraxial curvature radius of an image-side surface of the secondlens L2,r9: paraxial curvature radius of an object-side surface of the fifthlens L5, andr10: paraxial curvature radius of an image-side surface of the fifthlens L5.

It is not necessary to satisfy the above all conditional expressions,and by satisfying the conditional expression individually, operationaladvantage corresponding to each conditional expression can be obtained.

The imaging lens according to the present embodiments shows furtherpreferable effect by satisfying the below conditional expressions (1a)to (19a).

15.00<νd3<32.00  (1a)

0.40<T2/T3<0.98  (2a)

0.80<r2/f<1.50  (3a)

−4.50<r9/r10<−2.50  (4a)

2.90<(T4/f)×100<9.25  (5a)

1.80<T2/T1<6.00  (6a)

1.20<T3/T4<4.50  (7a)

2.60<D1/D2<3.60  (8a)

1.00<r3/f<7.50  (9a)

0.50<r4/f<1.15  (10a)

−1.90<r9/f<−0.95  (11a)

0.22<r2/r3<1.00  (12a)

1.50<r3/r4<8.00  (13a)

1.66<Nd2  (14a)

1.60<Nd3<1.68  (15a)

TTL/EPd2.3  (16a)

−18.50<f45/f<−2.80  (17a)

5.50<(T2/f)×100<9.80  (18a)

0.50<D2/D3<0.72  (19a)

The signs in the above conditional expressions have the same meanings asthose in the paragraph before the preceding paragraph.

In this embodiment, the aspheric shapes of the aspheric surfaces of thelens are expressed by Equation 1, where Z denotes an axis in the opticalaxis direction, H denotes a height perpendicular to the optical axis, Rdenotes a paraxial curvature radius, k denotes a conic constant, and A4,A6, A8, A10, A12, A14, A16, A18 and A20 denote aspheric surfacecoefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R^{2\;}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}} + {A_{18}H^{18}} + {A_{20}H^{20}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, examples of the imaging lens according to this embodiment will beexplained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, ih denotes a maximum image height, and TTL denotes atotal track length. Additionally, i denotes surface number counted fromthe object side, r denotes the paraxial curvature radius, d denotes thedistance of lenses along the optical axis (surface distance), Nd denotesa refractive index at d-ray (reference wavelength), and νd denotes anabbe number at d-ray. As for aspheric surfaces, an asterisk (*) is addedafter surface number i.

Example 1

The basic lens data is shown below in Table 1.

TABLE 1 Example1 Unit mm f = 3.91 Fno = 1.80 ω(°) = 39.2

 = 3.28 TTL = 4.44 Surface Data Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.48142*

55.86 (νd1) 3*

0.1193 4* 23.3810 0.2050 1.671 19.48 (νd2) 5* 3.8547 0.2914 6*

0.3060 1.614

 (νd3) 7* −100.0000

8* −6.0523 0.6147

55.86 (νd4) 9* −1.2303 0.2193 10* 

0.4724

 (νd5) 11*  1.4822 0.3000 18  Infinity 0.2100 1.517 64.20 19  Infinity

Image Plane Infinity Constituent Lens Data Start Focal Composite FocalEntrance pupil Lens Surface Length Length diameter 1 2 3.193 f45 −17.796Epd 2.171 2 4

3 6 20.844 4 8

5 10 −2.052 Aspheric Surface Data Second Surface Third Surface FourthSurface Fifth Surface k

0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 1 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at each wavelength of F-ray (486 nm),d-ray (588 nm), and C-ray (656 nm). The astigmatism diagram shows theamount of aberration at d-ray on a sagittal image surface S (solid line)and on tangential image surface T (broken line), respectively (same asFIGS. 4, 6, 8, 10, 12, 14 and 16). As shown in FIG. 2, each aberrationis corrected excellently.

Example 2

The basic lens data is shown below in Table 2.

TABLE 2 Example2 Unit mm f = 3.93 Fno = 1.80 ω(°) = 39.2

 = 3.28 TTL = 4.48 Surface Data Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.47562*

0.6470 1.544 55.86 (νd1) 3* 4.9230 0.1222 4* 15.3559 0.2050 1.571 19.48(νd2) 5* 3.7822 0.2960 6* 9.7439 0.3100 1.561

 (νd3) 7* 15.1618 0.5665 8* −7.2545 0.6402 1.544 55.86 (νd4) 9* −1.15990.1821 10*  −4.8616 0.4710 1.535

 (νd5) 11*  1.4023 0.3000 18  Infinity 0.2100 1.517

19  Infinity

Image Plane Infinity Constituent Lens Data Start Focal Composite FocalEntrance pupil Lens Surface Length Length diameter 1 2 3.254 f45 −33.810Epd 2.184 2 4 −7.528 3 6 40.340 4 8 2.448 5 10 −1.985 Aspheric SurfaceData Second Surface Third Surface Fourth Surface Fifth Surface k

0.000000E+00 1.000008E+01

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E−01 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 2 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4, eachaberration is corrected excellently.

Example 3

The basic lens data is shown below in Table 3.

TABLE 3 Example3 Unit mm f = 3.94 Fno = 1.80 ω(°) = 39.3

 = 3.26 TTL = 4.48 Surface Data Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.46412* 1.3958 0.6900 1.544 55.86 (νd1) 3* 5.3821 0.1204 4* 13.2526 0.20501.671 19.48 (νd2) 5* 3.4045 0.2908 6* 8.7789 0.3100 1.661 20.37 (νd3) 7*15.3108 0.5480 8* −7.2178 0.6337 1.544

 (νd4) 9* −1.0795 0.1527 10*  −5.0543 0.4559 1.535

 (νd5) 11*  1.2831 0.3000 18  Infinity 0.2100 1.517 64.20 19  Infinity

Image Plane Infinity Constituent lens Data Start Facet Composite FocalEntrance pupil Lens Surface Length Length diameter 1 2 3.253 f45 −60.434Epd 2.186 2 4

3 6 30.543 4 8 2.250 5 16

Aspheric Surface Data Second Surface Third Surface Fourth Surface FifthSurface k

0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 3 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6, eachaberration is corrected excellently.

Example 4

The basic lens data is shown below in Table 4.

TABLE 4 Example4 Unit mm f = 3.94 Fno = 1.80 ω(°) = 39.3

 = 3.25 TTL = 4.48 Surface Date Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.51722* 1.3535 0.6868 1.544 55.86 (νd1) 3* 4.9422 0.0888 4* 6.4427 0.20501.671 19.48 (νd2) 5* 2.9394 0.3834 6* Infinity

1.661 20.37 (νd3) 7* Infinity 0.4324 8* −8.7094  0.7383 1.544

 (νd4) 9* −1.1450  0.1568 10*  −5.0930  0.4397 1.535

 (νd5) 11*  1.3158 0.3000 18  Infinity 0.2100 1.517 64.20 19  Infinity0.5614 Image Plane Infinity Constituent Lens Date Start Focal CompositeFocal Entrance pupil Lens Surface Length Length diameter 1 2 3.208 f45−43.048 EPd 2.186 2 4 −8.245 3 6 Infinity 4 8 2.341 5 10 −1.904 AsphericSurface Date Second Surface Third Surface Fourth Surface Fifth Surface k−3.

E−01  0.

E+00  5.

E−01 −5.

E+00 A4 −2.

E−02 −1.

E−01 −1.

E−01 −4.

E−02 A6  2.

E−01 −1.

E−01  4.

E−01  3.

E−01 A8 −8.

E−01 −1.

E−01 −7.

E−01 −1.

E−01 A10  1.

E+00  2.

E−02  7.

E−01 −9.

E−01 A12 −1.

E+00  2.

E−01 −4.

E−01  3.

E+00 A14  1.

E+00 −3.

E−01 −8.

E−02 −4.

E+00 A16 −2.

E−01  1.

E−01  1.

E−01  2.

E+00 A18 0.000000E+00    0.000000E+00    0.000000E+00    0.000000E+00   A20 0.000000E+00    0.000000E+00    0.000000E+00    0.000000E+00   Aspheric Surface Date Seventh Surface Eighth Surface Ninth Surface kSixth Surface 0.000000E+00 0.000000E+00

A4 0.000000E+00

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 4 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8, eachaberration is corrected excellently.

Example 5

The basic lens data is shown below in Table 5.

TABLE 5 Example5 Unit mm f = 3.93 Fno = 2.00 ω(°) = 39.3

 = 3.26 TTL = 4.48 Surface Date Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.4.532* 1.3304 0.6315 1.544 55.86 (νd1) 3* 4.6353 0.0854 4* 5.7178 0.20501.671 19.48 (νd2) 5* 2.7845 0.3812 6* Infinity 0.2914 1.661 20.37 (νd3)7* Infinity 0.4429 8* −9.6211  0.7331 1.544 55.86 (νd4) 9* −1.1825 0.1555 10*  −4.4413  0.5609 1.535 55.86 (νd5) 11*  1.3938 0.3000 18 Infinity 0.2100 1.617 64.20 19  Infinity 0.5510 Image Plane InfinityConstituent Lens Data Start Focal Composite Focal Entrance pupil LensSurface Length Length diameter 1 2 3.212 f45 −37.225 EPd 1.905 2 4−8.318 3 6 Infinity 4 8 2.403 5 10 −1.919 Aspheric Surface Data SecondSurface Third Surface Fourth Surface Fifth Surface k

0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

q

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 5 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 10 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 5. As shown in FIG. 10,each aberration is corrected excellently.

Example 6

The basic lens data is shown below in Table 6.

TABLE 6 Example6 Unit mm f = 3.89 Fno = 2.00 ω(°) = 39.5

 = 3.26 TTL = 4.39 Surface Data Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.41702* 1.2500 0.6125 1.544 55.85 (νd1) 3* 4.7872 0.0676 4* 6.5821 0.20501.671 19.48 (νd2) 5* 2.8705 0.3313 6* Infinity 0.2929 1.661 20.37 (νd3)7* Infinity 0.3413 8* −6.2969  0.9198 1.544 55.85 (νd4) 9* −1.1481 0.1700 10*  −4.1481  0.4848 1.535 55.86; (νd5) 11*  1.4322 0.3000 18 Infinity 0.2100 1.517

19  Infinity 0.5250 Image Plane Infinity Constituent Lens Data StartFocal Composite Focal Entrance pupil Lens Surface Length Length diameter1 2 2.929 f45 −15.000 EFd 1.946 2 4 −7.754 3 6 Infinity 4 3 2.525 5 10−1.932 Aspheric Surface Data Second Surface Third Surface Fourth SurfaceFifth Surface k

0.000000E+00 1.00000E+01

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 6 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 12 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 6. As shown in FIG. 12,each aberration is corrected excellently.

Example 7

The basic lens data is shown below in Table 7.

TABLE 7 Example7 Unit mm f = 3.84 Fno = 2.00 ω(°) = 39.9

 = 3.26 TTL = 4.24 Surface Date Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.40392* 1.2331 0.5926 1.544 55.86 (νd1) 3* 4.4593 0.0832 4* 7.1198 0.20501.671 19.48 (νd2) 5* 3.0207 0.2947 6* Infinity 0.3167 1.661 20.37 (νd3)7* Infinity 0.4208 8* −3.7380  0.8692 1.544 55.86 (νd4) 9* −1.1355 0.2550 10*  −4.9685  0.4149 1.535 55.86 (νd5) 11*  1.5299 0.3000 18 Infinity 0.2100 1.517 54.20 19  Infinity 0.5513 Image Plane InfinityConstituent Lens Data Start Focal Composite Focal Entrance pupil LensSurface Length Length diameter 1 2 2.941 f45 −18.150 EPd 1.919 2 4−7.975 3 6 Infinity 4 8 2.747 5 10 −2.140 Aspheric Surface Data SecondSurface Third Surface Fourth Surface Fifth Surface k

0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 7 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 14 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 7. As shown in FIG. 14,each aberration is corrected excellently.

Example 8

The basic lens data is shown below in Table 8.

TABLE 8 Example8 Unit mm f = 3.88 Fno = 2.00 ω(°) = 39.7

 = 3.25 TTL = 4.24 Surface Data Surface Curvature Surface RefractiveAbbe Number

Radius

Distance

Index Nd Number νd (Object) Infinity Infinity 1 (stop) Infinity −0.42242* 1.8185 0.6058 1.544 55.86 (νd1) 3* 4.1789 0.0810 4* 7.3958 0.20681.871 19.48 (νd2) 5* 3.1132 0.3163 6* Infinity 0.2923 1.861 20.37 (νd3)7* Infinity 0.4177 8* −3.1765 0.6512 1.544 55.86 (νd4) 9* −1.1894 0.324810*  −5.7306 0.4000 1.535

 (νd5) 11* 

0.3000 18  Infinity 0.2100 1.517 64.20 19  Infinity 0.5073 Image PlaneInfinity Constituent Lens Data Start Focal Composite Focal Entrancepupil Lens Surface Length Length diameter 1 2 2.947 f45 −15.659 EPd1.932 2 4 −8.166 3 8 Infinity 4 8 3.132 5 10 −2.362 Aspheric SurfaceData Second Surface Third Surface Fourth Surface Fifth Surface k

0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 Aspheric Surface Data SixthSurface Seventh Surface Eighth Surface Ninth Surface k 0.000000E+000.000000E+00 0.000000E+00

A4

A6

A8

A10

A12

A14

A16

A18

A20

Tenth Surface Eleventh Surface k

A4

A6

A8

A10

A12

A14

A16

A18

A20

indicates data missing or illegible when filed

The imaging lens in Example 8 satisfies conditional expressions (1) to(19) as shown in Table 9.

FIG. 16 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 8. As shown in FIG. 16,each aberration is corrected excellently.

In table 9, values of conditional expressions (1) to (19) related to theExamples 1 to 8 are shown.

TABLE 9 Conditional expression Example1 Example2 Example3 Example4Example5 Example6 Example7 Example8  (1) νd3 25.58 20.37 20.37 20.3720.37 20.37 20.37 20.37  (2) T2/T3 0.51 0.52 0.53 0.89 0.86 0.97 0.700.76  (3) r2/1 1.37 1.25 1.37 1.26 1.18 1.23 1.16 1.08  (4) r9/r10 −3.17−3.48 −3.94 −3.87 −3.19 −2.90 −3.25 −3.45  (5) (T4/f) × 100 5.61 4.633.88 3.98 3.96 4.37 6.64 6.41  (6) T2/T1 2.44 2.42 2.41 4.32 4.46 4.903.54 3.90  (7) T3/T4 2.58 3.11 3.59 2.78 2.85 2.01 1.65 1.29  (8) D1/D23.19 3.16 3.37 3.35 3.08 2.99 2.69 2.95  (9) r3/f 5.98 3.91 3.37 1.641.45 1.69 1.85 1.91 (10) r4/f 0.99 0.96 0.87 0.75 0.71 0.74 0.79 0.81(11) r9/f −1.20 −1.24 −1.28 −1.29 −1.13 −1.07 −1.29 −1.48 (12) r2/r30.23 0.32 0.41 0.77 0.81 0.73 0.63 0.57 (13) r3/r4 6.07 4.06 3.89 2.192.05 2.29 2.36 2.39 (14) Nd2 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67(15) Nd3 1.61 1.66 1.66 1.66 1.66 1.66 1.66 1.66 (I6) TTL/EPd 2.05 2.052.05 2.05 2.28 2.28 2.21 2.20 (17) f45/f −4.55 −10.08 −15.36 −10.94−9.47 −3.85 −4.73 −4.05 (18) (T2/f) × 100 7.46 7.53 7.39 9.74 9.70 6;.517.88 8.19 (19) D2/D3 0.67 0.66 0.66 0.66 0.70 0.70 0.65 0.70

When the imaging lens according to the present invention is adopted to aproduct with the camera function, there is realized contribution to thewide field of view, the low-profileness and the low F-number of thecamera and also high performance thereof.

DESCRIPTION OF REFERENCE NUMERALS

-   ST: aperture stop-   L1: first lens-   L2: second lens-   L3: third lens-   L4: fourth lens-   L5: fifth lens-   ih: maximum image height-   IR: filter-   IMG: imaging plane

1. An imaging lens comprising in order from an object side to an imageside, a first lens with positive refractive power having a convexsurface facing the object side near an optical axis, a second lenshaving negative refractive power near the optical axis, a third lens, afourth lens, and a fifth lens with the negative refractive power havinga concave surface facing the image side near the optical axis, whereinan image-side surface of said fifth lens is formed as an asphericsurface having at least one pole point in a position off the opticalaxis, and below conditional expressions (1), (2), (3) and (4) aresatisfied:10.00<νd3<39.00  (1)0.25<T2/T3<1.00  (2)0.50<r2/f<1.65  (3)−5.00<r9/r10<−2.20  (4) where νd3: an abbe number at d-ray of the thirdlens, T2: a distance along the optical axis from an image-side surfaceof the second lens to an object-side surface of the third lens, T3: adistance along the optical axis from an image-side surface of the thirdlens to an object-side surface of the fourth lens, r2: paraxialcurvature radius of an image-side surface of the first lens, f: a focallength of the overall optical system of the imaging lens, r9: paraxialcurvature radius of an object-side surface of the fifth lens, and r10:paraxial curvature radius of an image-side surface of the fifth lens. 2.An imaging lens comprising in order from an object side to an imageside, a first lens with positive refractive power having a convexsurface facing the object side near an optical axis, a second lenshaving negative refractive power near the optical axis, a third lens, afourth lens, and a fifth lens with the negative refractive power havinga concave surface facing the image side near the optical axis, whereinan image-side surface of said fifth lens is formed as an asphericsurface having at least one pole point in a position off the opticalaxis, an image-side surface of said first lens is a concave surfacefacing the image side near the optical axis, an object-side surface ofsaid second lens is a convex surface facing the object side near theoptical axis, said fourth lens has the positive refractive power nearthe optical axis, composite refractive power of said fourth lens andsaid fifth lens is negative near the optical axis, and below conditionalexpressions (1) and (4) are satisfied:10.00<νd3<39.00  (1)−5.00<r9/r10<−2.20  (4) where νd3: an abbe number at d-ray of the thirdlens, r9: paraxial curvature radius of an object-side surface of thefifth lens, and r10: paraxial curvature radius of an image-side surfaceof the fifth lens.
 3. The imaging lens according to claim 1, whereinsaid fourth lens and said fifth lens has negative composite refractivepower near the optical axis.
 4. The imaging lens according to claim 1,wherein an object-side surface of said second lens is a convex surfacefacing the object side near the optical axis.
 5. The imaging lensaccording to claim 1, wherein a below conditional expression (5) issatisfied:1.90<(T4/f)×100<10.00  (5) where T4: a distance along the optical axisfrom an image-side surface of the fourth lens to an object-side surfaceof the fifth lens, and f: a focal length of the overall optical systemof the imaging lens.
 6. The imaging lens according to claim 2, wherein abelow conditional expression (6) is satisfied:1.20<T2/T1<7.00  (6) where T2: a distance along the optical axis from animage-side surface of the second lens to an object-side surface of thethird lens, and T1: a distance along the optical axis from an image-sidesurface of the first lens to an object-side surface of the second lens.7. The imaging lens according to claim 1, wherein a below conditionalexpression (7) is satisfied:1.10<T3/T4<5.50  (7) where T3: a distance along the optical axis from animage-side surface of the third lens to an object-side surface of thefourth lens, and T4: a distance along the optical axis from animage-side surface of the fourth lens to an object-side surface of thefifth lens.
 8. The imaging lens according to claim 2, wherein a belowconditional expression (8) is satisfied:2.30<D1/D2<3.80  (8) where D1: a thickness along the optical axis of thefirst lens, and D2: a thickness along the optical axis of the secondlens.
 9. The imaging lens according to claim 2, wherein a belowconditional expression (9) is satisfied:0.50<r3/f<9.00  (9) where r3: paraxial curvature radius of anobject-side surface of the second lens, and f: a focal length of theoverall optical system of the imaging lens.
 10. The imaging lensaccording to claim 1, wherein a below conditional expression (10) issatisfied:0.35<r4/f<1.25  (10) where r4: paraxial curvature radius of animage-side surface of the second lens, and f: a focal length of theoverall optical system of the imaging lens.
 11. The imaging lensaccording to claim 2, wherein a below conditional expression (11) issatisfied:−2.30<r9/f<−0.85  (11) where r9: paraxial curvature radius of anobject-side surface of the fifth lens, and f: a focal length of theoverall optical system of the imaging lens.
 12. The imaging lensaccording to claim 1, wherein a below conditional expression (12) issatisfied:0.20<r2/r3<1.30  (12) where r2: paraxial curvature radius of animage-side surface of the first lens, and r3: paraxial curvature radiusof an object-side surface of the second lens.
 13. The imaging lensaccording to claim 1, wherein a below conditional expression (13) issatisfied:1.00<r3/r4<9.50  (13) where r3: paraxial curvature radius of anobject-side surface of the second lens, and r4: paraxial curvatureradius of an image-side surface of the second lens.
 14. The imaging lensaccording to claim 1, wherein said second lens and said third lens aremade of a plastic material, and below conditional expressions (14) and(15) are satisfied:1.65<Nd2  (14)1.60<Nd3<1.70  (15) where Nd2: refractive index at d-ray of the secondlens, and Nd3: refractive index at d-ray of the third lens.
 15. Theimaging lens according to claim 1, wherein a below conditionalexpression (16) is satisfied:TTL/EPd<2.50  (16) where TTL: a total track length, and EPd: an entrancepupil diameter.
 16. The imaging lens according to claim 2, wherein abelow conditional expression (10) is satisfied:0.35<r4/f<1.25  (10) where r4: paraxial curvature radius of animage-side surface of the second lens, and f: a focal length of theoverall optical system of the imaging lens.
 17. The imaging lensaccording to claim 2, wherein a below conditional expression (12) issatisfied:0.20<r2/r3<1.30  (12) where r2: paraxial curvature radius of animage-side surface of the first lens, and r3: paraxial curvature radiusof an object-side surface of the second lens.
 18. The imaging lensaccording to claim 2, wherein a below conditional expression (13) issatisfied:1.00<r3/r4<9.50  (13) where r3: paraxial curvature radius of anobject-side surface of the second lens, and r4: paraxial curvatureradius of an image-side surface of the second lens.
 19. The imaging lensaccording to claim 2, wherein said second lens and said third lens aremade of a plastic material, and below conditional expressions (14) and(15) are satisfied:1.65<Nd2  (14)1.60<Nd3<1.70  (15) where Nd2: refractive index at d-ray of the secondlens, and Nd3: refractive index at d-ray of the third lens.
 20. Theimaging lens according to claim 2, wherein a below conditionalexpression (16) is satisfied:TTL/EPd<2.50  (16) where TTL: a total track length, and EPd: an entrancepupil diameter.